Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to an in-cell touch liquid crystal display device having a pixel electrode top structure and a method for manufacturing the same.
Discussion of the Related Art
A touch screen has been used, which may allow a user to directly input information on a screen by using a finger or pen instead of a mouse or keyboard conventionally used as an input device of a flat panel display device or a key pad used as an input device of portable electronic equipment. The touch screen has an advantage in that anyone may easily manipulate it, and thus its application has been increased.
Such a touch screen has been applied to monitors such as a navigation system, an industrial terminal, a notebook computer, a banking automated teller machine (ATM), and a game machine, portable terminals such as a cellular phone, MP3, PDA, PMP, PSP, a portable game machine, a DMB receiver, and a tablet PC, and home appliances such as a refrigerator, a microwave oven, and a washing machine.
The touch screen may be categorized into an in-cell touch type where a touch screen is built in a cell of a liquid crystal panel, an on cell touch type where a touch screen is formed on a cell of a liquid crystal panel, and an add on type where a touch screen is combined with an outside of a display panel, in accordance with a structure combined with a liquid crystal panel. Hereinafter, a touch screen (touch panel) combined with a liquid crystal panel will be referred to as a ‘touch display device.’
FIGS. 1A, 1B and 1C illustrate a touch display device according to the related art to which a touch screen is applied. FIG. 1A illustrates a touch display device of an add on type, FIG. 1B illustrates a touch display device of a modified add on type, and FIG. 1C illustrates a touch display device of a hybrid type.
In the touch display device of the add on type in FIG. 1A and the modified add on type in FIG. 1B, a touch screen is arranged on a liquid crystal panel that includes a thin film transistor (TFT) array substrate 1 and a color filter array substrate 2. A touch driving electrode TX and a touch receiving electrode RX are arranged on the touch screen. At this time, the touch driving electrode TX and the touch receiving electrode RX may be arranged on their respective layers different from each other, or may be arranged on the same layer as each other.
In the touch display device of the hybrid type in FIG. 1C, a touch driving electrode TX is arranged on a TFT array substrate 1, and a touch receiving electrode RX is arranged on a color filter array substrate 2.
Since the liquid crystal panel and the touch screen of the touch display device according to the related art should be manufactured separately, a problem occurs in that a manufacturing process is complicated and its cost is increased.
Recently, in order to reduce a thickness of the touch display device and save its manufacturing cost, an in-cell touch liquid crystal display device has been developed, in which a touch electrode (touch sensor) is built in a cell of a liquid crystal panel. In the in-cell touch liquid crystal display device, a common electrode arranged on a TFT array substrate of the liquid crystal panel is used as a touch sensor.
FIG. 2 illustrates an in-cell touch liquid crystal display device of a mutual capacitive type.
Referring to FIG. 2, the in-cell touch liquid crystal display device of a mutual capacitive type drives a common electrode arranged on a TFT array substrate of a liquid crystal panel 10 as a touch driving electrode TX and a touch receiving electrode RX. This mutual capacitive type has a problem in that a bezel width is increased as a touch driving line 14 and a touch receiving line 12 are arranged on left and right bezel areas of the liquid crystal panel 10.
FIG. 3 illustrates a manufacturing process of an in-cell touch display device of a common electrode Vcom top type, and also illustrates the number of masks required for the manufacturing process.
Referring to FIG. 3, a common electrode Vcom top pixel structure is applied to the in-cell touch liquid crystal display device according to the related art V. In the common electrode Vcom top pixel structure, a common electrode is arranged on an uppermost layer, and a pixel electrode is arranged below the common electrode.
In the in-cell touch liquid crystal display device according to the related art in which a low temperature poly silicon (LTPS) is used as a material of an active layer of a TFT and to which the common electrode Vcom top pixel structure is applied, 11 masks are required for a process for manufacturing the in-cell touch liquid crystal display device.
As described above, if the common electrode Vcom top pixel structure is applied to the in-cell touch liquid crystal display device according to the related art, light transmittance is high at an edge portion of pixels, whereby a problem occurs in that mixed colors are generated among red, green and blue pixels.